Re: CVE Request: Linux kernel execution in the early microcode loader.

[Florian Weimer <fweimer () redhat com>]

On 03/18/2015 01:25 PM, Quentin Casasnovas wrote:
> The attack vector could be from anyone between Intel and people
> shipping/packaging the microcode, or could potentially be used to get a
> resilient backdoor on system already compromised by sticking a tampered
> microcode on the initrd.  It would also allow root to get kernel execution
> by recreating the initrd.  I admit these are overly paranoid scenarios, but
> I _think_ there's still a privilege crossing from root to kernel exec which
> could make sense on certain security model.

Yes, Secure Boot separates root privileges from code execution in ring 0
(according to some interpretations of Secure Boot, in practice,
signatures on binaries allowing ring 0 code execution are not revoked,
so this new vulnerability does not alter the general picture).

-- 
Florian Weimer / Red Hat Product Security